Boat docks at Lake Merritt. A sign portruding from the water cautions people that there's a "steep drop off" beneath the surface.
The docks of the Lake Merritt Rowing Club. September 1, 2020. Photo: Pete Rosos

On a hot summer day, Lake Merritt’s deep blue waters look downright inviting. And it seems like every year one or two people throw caution to the wind, jump in, and swim out toward the center. This year is no exception. Already we’ve seen a pair of people taking a leisurely swim in the Glen Echo arm, and a young man coated head to toe in peanut butter step trepidatiously into the water near Lakeshore Avenue before plunging in.

It should go without saying that no one should swim in Lake Merritt. It’s a wildlife refuge and swimming can disturb birds and other creatures that make their homes there. It’s also polluted by oil, trash, chemicals, and other runoff from the streets and storm drains that empty into it.

But with weeks more of warm weather ahead of us, there’s a good chance someone else will succumb to the lake’s siren song and take a dip. After all, there’s a long history of Oaklanders enjoying Lake Merritt as a swimming hole. As a public service, The Oaklandside looked into reasons why swimming in the lake isn’t a good idea.

What’s the story with Lake Merritt?

Lake Merritt’s blue waters can look downright inviting many days of the year. Credit: Darwin BondGraham

For starters, Lake Merritt isn’t really a lake. It is a tidal slough, which is basically a wetland channel  connected to the ocean. Its water is a mixture of freshwater from creeks that drain from the hills and seawater from the Bay. The “lake” has likely existed for thousands of years. Long before Oakland was founded the Ohlone fished and hunted in the wetlands surrounding the lagoon. Lake Merritt continues to be an important place for Ohlone people.

But the lake started to get trashed after Oakland was incorporated in 1852. Residents pumped in raw sewage from their homes and businesses and it became a sink for litter swept off of surrounding streets. In 1869, Mayor Samuel Merritt paid to erect a dam at the 12th Street Bridge across the neck of the inlet, which limited the flow of tides into the lake. Starting in the 1890s, the lake was continuously dredged to fill in the surrounding mud flats.

The result was that Lake Merritt’s water became fetid, murky, and stinky. But people continued to swim in it. Newspapers from the late 1800s are filled with references of people recreating in the lake. For example, in 1890 Captain Jack Williams, a famous adventurer, put on a show for several thousand Oaklanders by swimming across Lake Merritt with his feet and legs tied together and his arms bound to his sides, so that he had to propel himself like a snake, according to the Oakland Tribune. In 1901, the city held a rowing and swimming regatta in which dozens of people competed in relay races across the lagoon, according to the San Francisco Call.

An article from 1890 advertising a swimming feat in Lake Merritt. Credit: Courtesy of Oakland Tribune/

However, Oakland outlawed swimming in Lake Merritt in 1912 due to pollution and because people were changing their clothes in lakeside bushes, which was viewed as indecent at the time. 

By the 1920s, the Fish and Game Commission advised people not to swim in the lake due to high bacterial levels. 

The fantasy of transforming Lake Merritt into a giant swimming pool persisted for the next couple of decades. Mayor John Davie toyed with the idea of pumping clean saltwater from the bay into a portion of the lake to create a designated swimming area. In 1938, the City Council considered a proposal to make a section of the lake swimmable. But councilmembers balked at the project’s estimated $300,000 price tag, about $9 million today. 

Oakland officials eventually gave up on the idea of restoring the water quality in the lake so that people could enjoy it and instead focused on beautifying the area around the lake and dredging the water to remove polluted sediments. By the early 1990s, the water quality improved to the point where body contact sports would be allowed in the lake based on bacterial counts, according to the Lake Merritt Institute. Today, people row and sail small boats in the lake, bringing them into limited contact with the water.

But the presence of trash and low oxygen levels led the Environmental Protection Agency to label the lake as an “impaired body of water” in 1999. That designation remains in place, according to the EPA’s website.

Bird poop, bacteria, algae, and no lifeguards

A seagull comes in for a landing on Lake Merritt by a dock. September 1, 2020. Photo: Pete Rosos

Oakland’s prudish government hasn’t softened its stance on swimming in the lake. According to Section 9.08.090 of the city’s municipal code, it is against the law to bathe or swim in Lake Merritt. However, it is legal to swim in the San Antonio estuary and Oakland Harbor—the water between Oakland and Alameda—provided one is wearing a bathing suit. Whether that’s safe is a question beyond the scope of this article. 

If OPD catches you swimming in Lake Merritt the department can issue a citation. But it’s unclear what penalty that carries, or if OPD has enforced this law recently. The department said it would require a public records request to disclose how many incidents have been reported of people swimming in the lake. In 2016, police responded to reports of a man swimming in the lake and detained him for a psychiatric evaluation

Swimming really hasn’t been much of a nuisance for the city for a long time. You have to go back to the 1930s to find accounts of the police and city cracking down in a big way on swimming in the lake. According to a 1932 article in the Tribune, “au naturel” night swimming parties of naked boys drew the ire of Police Captain Frank Lynch, who vowed to enforce the swimming ban.

A newspaper article from 1932 about enforcing the ban on swimming in Lake Merritt. Credit: Courtesy of Oakland Tribune/

From a public health perspective, there are some good reasons not to swim in Lake Merritt.

Perhaps the most important thing to consider is that Oakland doesn’t have the resources to ensure the safety of anyone swimming in the lake: there are no lifeguards on duty and there are no designated beaches or roped-off areas for swimming. Much of the lake is shallow, but drowning is still a very real risk. 

Lake Merritt is a bird sanctuary, so depending on the season, there will be a lot of bird poop in the water. Mostly because of this, the lake sees fluctuating levels of the bacteria E. coli. Most types of this bacteria are not necessarily dangerous. But the average swimmer probably doesn’t want to get coated in liquid bird poop and ingesting it may give you stomach problems.

E. coli can also serve as an indicator that other toxic pathogens are lurking in the water. Because storm drains feed into Lake Merritt, human and dog poop have been known to wash in. In 2019, volunteer monitors working with the Environmental Protection Agency reported high levels of E. coli in various parts of the lake. 

A city spokesperson said the water quality of the lake is regularly monitored and is in general safe for occasional body contact “but not recommended for recreational swimming, which greatly increases the risk of ingestion of water.”

The lake is also filled with algae. Anyone who’s walked along the edge of the lake has seen this green, slimy substance clinging to rocks. Richard Bailey, founder of the Lake Merritt Institute, said this stuff is icky but it’s not going to harm a swimmer.

“There are types of algal plankton that can be poisonous,” Bailey said, describing plankton species that have caused shellfish and crab fisheries to shut down. “But we don’t get that type in the lake—it’s too warm for that.”

Bailey said the lake does occasionally get algae blooms caused by a flood of nutrients, such as from fertilizer runoff. A bloom can cause a rapid decline in oxygen levels, making it deadly to aquatic critters. Last August, a bloom in Lake Merritt killed thousands of fish.

Bailey said swimming through last year’s bloom, which consisted of the algae species Heterosigma akashiwo, would have been unsafe because it was possibly emitting toxins. He said the lake also occasionally experiences blooms of green algae.  Swimming through those blooms would be unpleasant for a person, but not deadly. Generally, you run the risk of getting an infection in your eyes, ears, or throat.

“I don’t think anybody is going to die from swimming in the lake,” Bailey said. “But it’s not a good idea—you’re better off in a swimming pool.”

Oakland recently installed a surface aerator—similar to a fountain—near the Pergola and Colonnade to churn the water and dissolve more oxygen into the lake. The device will hopefully give the lake’s aquatic denizens a better shot at survival if another algae bloom causes the oxygen levels to drop.

But aerators can only improve conditions in a small area and they won’t address the bigger contaminant in the lake: trash. Dozens of storm drains feed into the lake, and after a strong rainfall, all sorts of debris is washed from downtown into the water.

Eli Kersh of LakeTech, an Oakland company that installed the aerator, said he’d never swim in the lake, citing concerns about stepping on needles buried in the mud. But he also pointed out that swimmers would potentially be exposed to residue from oils, brake dust, fertilizer, pesticide, and other chemicals that get flushed into the water.

“That’s just the nature of urban lakes,” Kersh said. “There’s nothing we can do about that.”

What’s it like to swim in the lake? We spoke to someone who braved the brackish waters

The Oaklandside tried to track down people who’ve recently swum in the lake, including the guy coated in peanut butter, but we couldn’t identify them. However, there is a video of this strange feat on Instagram.

We did find one person who has taken several dips in the lake. They requested anonymity because they’re concerned about being fined by the city and potential damage to their professional reputation.

This individual said that over a couple decades ago, when they were under age 18, they attended a sailing camp at Lake Merritt. As a celebration at the end of the sailing season, they and other kids would jump off the dock into the lake.

“It wasn’t weird, it wasn’t gross,” they said. “There wasn’t a stigma attached to jumping in the lake, even though it was probably nasty then.”

Years later, as a student at a local high school, this person was part of a group that participated in various risky stunts and embarrassing dares, which were ranked using a point system. The highest scoring dare was to swim across Lake Merritt. Having already jumped in the lake several times, this person decided to win the biggest prize.

They entered the water near the columns by Grand Avenue and swam across an arm of the lake. The swim only lasted 35 or 40 seconds, and the only negative thing they had to say about their experience was the disgusting sensation of stepping through the mud. They quickly rinsed off after the swim and said they experienced no unpleasant side effects.

“Maybe I was naïve, but I also had Oakland pride about it,” they said. “I was like, I can do this, I don’t care, it’s just in and out—don’t open your mouth.”

This person said they probably wouldn’t swim in the lake again, especially after hearing about last year’s algae bloom. But they were enthusiastic about the never-achieved dream of the lake one day becoming a haven for swimming like Lake Temescal or Lake Anza.

“If they could make it work that would be really cool,” they said.

Eli Wolfe reports on City Hall for The Oaklandside. He was previously a senior reporter for San José Spotlight, where he had a beat covering Santa Clara County’s government and transportation. He also worked as an investigative reporter for the Pasadena-based newsroom FairWarning, where he covered labor, consumer protection and transportation issues. He started his journalism career as a freelancer based out of Berkeley. Eli’s stories have appeared in The Atlantic,, Salon, the San Francisco Chronicle, and elsewhere. Eli graduated from UC Santa Cruz and grew up in San Francisco.